About two-thirds of global energy consumption occurs as hydrocarbon fuel combustion in boilers, furnaces, kilns, and turbines. A small percentage of consumption is provided by combustion of other fuels such as hydrogen and carbon monoxide. The energy released by the combustion is used to generate electrical power and to provide heat for a wide range of industrial and commercial purposes.
In conventional furnaces, boilers, process heaters, and the like, combustion air and fuel are supplied to a “burner assembly”. The part that outputs fuel to the combustion chamber is called a fuel nozzle (in the case of a non-premixing nozzle). Air can be forced air or natural draft. In many burner assemblies, the air and fuel are admitted in close proximity to one another. Another part of some conventional burner assemblies is a flame holder. Compared to usually-seen flames, the fuel and air velocities in an industrial burner assembly may tend to be too high to hold the flame against the fuel nozzle (or for the flame to be held in an equilibrium position where the flame speed is equal to the fuel and air velocity). A burner assembly manufacturer may therefore add an eddy-producing flame-holder structure to cause the flame to be held in a known position. In some burner assemblies, the flame holder is a refractory material that extends into the combustion chamber; such a refractory flame holder is often referred to as a burner tile.
This conventional structure works adequately but could be improved by reducing emissions and by improving the combustion process. It has been found by the inventors that electricity can be applied to the combustion reaction, and the characteristics of the combustion reaction can be selected according to electrode geometry and location, as well as electric signal characteristics (e.g., AC vs. DC, frequency, waveform sharpness, phase relationships, and voltage), to improve combustion. However, conventional devices may suffer from limited provisions for passing electrical signals, especially high-voltage signals, to the combustion chamber.